U.S. Pat. No.4,571,366 (Thomas and Tillman), assigned to Owens-Illinois, Inc., discloses a process for forming a doped oxide film and preparing a doped silicon semiconductor from the film. The process includes a polyorganosiloxane-dopant compound solution that is applied to a silicon wafer by a spin-on step. The resultant film is heated to provide a glassy dopant film that is further heated to impregnate the silicon wafer with the dopant including P, As or B. The glassy layer is then removed to provide the doped wafer. This patent (U.S. 4,571,366) is hereby incorporated by reference for the background information including the preparation of a doped silicon wafer and the method of testing the doped wafer including average Measured Resistances in Ohms/Square.
It is desirable, as an improvement in the art, to provide a powdery, easily applied film (merely applied by screen-printing) on the silicon wafer instead of having to form a glassy layer first. Hence, it is desirable to eliminate the use of the glassy layer and the accompanying diffusion tubes and spin-on equipment and thus provide a doping process suitable for a continuous process using a belt furnace.
It is also desirable to provide a doping process in which the doping film deposited on the silicon wafer is easily and quickly removed in a short time.
It is also desirable to provide a doping composition and method for doping a silicon wafer in which the composition is easily and efficiently deposited on the wafer, the resultant deposited doping film very easily removed, and the method resulting in a matte finish on the wafer surface, thereby eliminating a process step previously required to reduce the silicon surface reflectivity to produce a silicon surface for solar cells.